# MODBUS RTU communication time out faillure

**URL:** <https://forum.inductiveautomation.com/t/modbus-rtu-communication-time-out-faillure/41033>\
**Category:** Ignition Exchange\
**Tags:** ignition80\
**Created:** [November 29, 2020, 8:04pm UTC](https://forum.inductiveautomation.com/t/modbus-rtu-communication-time-out-faillure/41033 "2020-11-29T20:04:07Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![Matrix\_Engineering](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/matrix_engineering/32/19781_2.png) [@Matrix\_Engineering](https://forum.inductiveautomation.com/u/Matrix_Engineering)\
**Post date:** [November 30, 2020, 9:01am UTC](https://forum.inductiveautomation.com/t/modbus-rtu-communication-time-out-faillure/41033/2 "2020-11-30T09:01:47Z")

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You might get some ideas here:

> [@Modbus rtu over tcp read failure](http://forum.inductiveautomation.com/t/modbus-rtu-over-tcp-read-failure/35815/13):
>
> Your network load is not the problem. Based on your JSON export, most of your tags are contiguous, words 22-35, with three others: 6-7, 44-45, and 66-67. Ideally, you need four requests to read these blocks, satisfying the ten float tags. Per the modbus specification (PI-MBUS-300 from [modbus.org](http://modbus.org)) these requests and their responses should take 62.5ms at 19200-N-8-1 (including the inter-message silent time on the wire). Twenty devices is a modest overload–you won’t get one-second timing. I be…

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